US-12626411-B2 - Method and apparatus for adaptive quantization for UV attribute in symmetry mesh

Abstract

A method performed by an encoder comprises extracting from an input mesh an extracted half symmetry mesh, the input mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted mesh comprising only one of the first side and the second side; quantizing the extracted half symmetry mesh at a first bitdepth to generate a first quantized mesh; reparameterizing the first quantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh; quantizing the reparameterized mesh at a second bitdepth different from the first bitdepth to generate a second quantized mesh; and encoding the second quantized mesh into a bitstream.

Inventors

• Thuong NGUYEN CANH
• Xiaozhong Xu
• Shan Liu

Assignees

• Tencent America LLC

Dates

Publication Date

20260512

Application Date

20230914

Claims (18)

1. 1 . A method performed by at least one processor of an encoder, the method comprising: extracting from an input mesh an extracted half symmetry mesh, the input mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted mesh comprising only one of the first side and the second side; quantizing the extracted half symmetry mesh at a first bitdepth to generate a first quantized mesh; reparameterizing the first quantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh, the reparameterizing further comprising: linear reparameterization performing a linear transform on the first quantized mesh to reduce empty spaces in the first quantized mesh, and non-linear reparameterization performing a non-linear process on an output of the linear reparameterization; quantizing the reparameterized mesh at a second bitdepth different from the first bitdepth to generate a second quantized mesh; and encoding the second quantized mesh into a bitstream.
2. 2 . The method according to claim 1 , wherein the second bitdepth is less than the first bitdepth.
3. 3 . The method according to claim 1 , wherein the extracted half symmetry mesh is bounded by a first 2D bounding box that circumscribes the extracted mesh, the first 2D bounding box defined in a 2D space by (i) a first maximum coordinate and a first minimum coordinate in a first direction and (ii) a second maximum coordinate and a second minimum coordinate in a second direction orthogonal to the first direction.
4. 4 . The method according to claim 3 , wherein the quantizing the extracted half symmetry mesh is based on a first quantization step and the first bitdepth, and wherein the first quantization step is determined based on (i) a maximum of (a) a difference between the first maximum coordinate and the first minimum coordinate and (b) a difference between the second maximum coordinate and the second minimum coordinate and (ii) the first bitdepth.
5. 5 . The method according to claim 3 , wherein the extracted mesh is divided into M disconnected segments, wherein the reparameterizing comprises determining a transform for each disconnected segment that minimizes a total area of the extracted half symmetry mesh such that the reparameterized mesh defined by a second 2D bounding box that has an area smaller than an area of the first 2D bounding box.
6. 6 . The method according to claim 5 , wherein the second 2D bounding box is defined in the 2D space by (i) a third maximum coordinate and a third minimum coordinate in the first direction and (ii) a fourth maximum coordinate and a fourth minimum coordinate in the second direction.
7. 7 . The method according to claim 6 , wherein the quantizing the reparameterized mesh is based on a second quantization step and the second bitdepth, and wherein the second quantization step is determined based on (i) a maximum of (a) a difference between the third maximum coordinate and the third minimum coordinate and (b) a difference between the fourth maximum coordinate and the fourth minimum coordinate and (ii) the second bitdepth.
8. 8 . The method according to claim 5 , further comprising: determining for each determined transform for each segment, a corresponding inverse transform, and wherein the bitstream includes each determined inverse transform.
9. 9 . A method performed by at least one processor of an encoder, the method comprising: decoding a received bitstream to extract from an encoded mesh an extracted half symmetry mesh, the encoded mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted half symmetry mesh comprising one of the first side and the second side, dequantizing the extracted half symmetry mesh at a first bitdepth to generate a first quantized dequantized mesh, reparameterizing the first dequantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh, the reparameterizing further comprising: linear reparameterization performing a linear transform on the first dequantized mesh to reduce empty spaces in the first quantized mesh, and non-linear reparameterization performing a non-linear process on an output of the linear reparameterization, dequantizing the reparameterized mesh at a second bitdepth different from the first bitdepth to generate a second dequantized mesh, and reconstructing the encoded mesh based on the second dequantized mesh.
10. 10 . The method according to claim 9 , wherein the second bitdepth is less than the first bitdepth.
11. 11 . The method according to claim 9 , wherein the extracted half symmetry mesh is bounded by a first 2D bounding box that circumscribes the extracted mesh, the first 2D bounding box defined in a 2D space by (i) a first maximum coordinate and a first minimum coordinate in a first direction and (ii) a second maximum coordinate and a second minimum coordinate in a second direction orthogonal to the first direction.
12. 12 . The method according to claim 11 , wherein the dequantizing the extracted half symmetry mesh is based on a first quantization step and the first bitdepth, and wherein the first quantization step is determined based on (i) a maximum of (a) a difference between the first maximum coordinate and the first minimum coordinate and (b) a difference between the second maximum coordinate and the second minimum coordinate and (ii) the first bitdepth.
13. 13 . The method according to claim 11 , wherein the extracted mesh is divided into M disconnected segments, wherein the reparameterization further comprises determining a transform for each disconnected segment that minimizes a total area of the extracted half symmetry mesh such that the reparameterized mesh defined by a second 2D bounding box that has an area smaller than an area of the first 2D bounding box.
14. 14 . The method according to claim 13 , wherein the second 2D bounding box is defined in the 2D space by (i) a third maximum coordinate and a third minimum coordinate in the first direction and (ii) a fourth maximum coordinate and a fourth minimum coordinate in the second direction.
15. 15 . The method according to 14 , wherein the dequantizing the reparameterized mesh based on a second quantization step and the second bitdepth, and wherein the second quantization step is determined based on (i) a maximum of (a) a difference between the third maximum coordinate and the third minimum coordinate and (b) a difference between the fourth maximum coordinate and the fourth minimum coordinate and (ii) the second bitdepth.
16. 16 . The method according to claim 13 , wherein the bitstream includes at least one inverse transform.
17. 17 . A non-transitory computer readable medium storing a bitstream generated by a method comprising: extracting from an input mesh an extracted half symmetry mesh, the input mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted mesh comprising one of the first side and the second side; quantizing the extracted half symmetry mesh at a first bitdepth to generate a first quantized mesh; reparameterizing the first quantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh, the reparameterizing further comprising: linear reparameterization performing a linear transform on the first quantized mesh to reduce empty spaces in the first quantized mesh, and non-linear reparameterization performing a non-linear process on an output of the linear reparameterization; quantizing the reparameterized mesh at a second bitdepth different from the first bitdepth to generate a second quantized mesh; and encoding the second quantized mesh into the bitstream.
18. 18 . The non-transitory computer readable medium according to claim 17 , wherein the second bitdepth is less than the first bitdepth.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority from U.S. Provisional Application No. 63/423,260 filed on Nov. 7, 2022, the disclosure of which is incorporated herein by reference in its entirety. FIELD This disclosure is directed to a set of advanced video coding technologies. More specifically, the present disclosure is directed to adaptive quantization for UV attributes in a symmetry mesh. BACKGROUND VMesh is an ongoing MPEG standard to compress meshes. The current VMesh reference software compresses meshes based on decimated base meshes, displacements vectors, and motion fields. The displacements are calculated by searching the closest point on the input mesh with respect to each vertex of the subdivided based mesh. The displacement vectors are transformed into wavelet coefficients by a linear lifting scheme, and then the coefficients are quantized and coded by a video codec or an arithmetic codec. Unfortunately, only local characteristic of mesh is utilized to compress the mesh but not global characteristics like symmetry. Reflection symmetry is a popular characteristic of mesh encoding, especially computer generated meshes. Symmetry may be utilized to compress symmetry mesh. Vertices are divided into a left and a right part of a symmetry plane. The left part is encoded by mesh coding while the right part is encoded by a symmetry prediction and displacement coding. UV attributes may display a certain level of symmetry. Reparameterization of UV attributes may be performed by re-arranging and/or regenerating a UV map and associated texture map. Reparameterization may be performed to improve lossy mesh compression performance. In general, a decimation process may be applied and followed up by reparameterization such as UV Atlas as in VMesh. UVAtlas is very efficient for fragmented UV attributes. However, these techniques do not provide an effective method to quantize a symmetry UV. Furthermore, these techniques to not provide a method to reparametrize UV attributes for lossless and lossy compression. Additionally, these methods to reparameterize UV without modifying the associated texture. SUMMARY According to one or more embodiments, a method performed by at least one processor of an encoder comprises extracting from an input mesh an extracted half symmetry mesh, the input mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted mesh comprising only one of the first side and the second side; quantizing the extracted half symmetry mesh at a first bitdepth to generate a first quantized mesh; reparameterizing the first quantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh; quantizing the reparameterized mesh at a second bitdepth different from the first bitdepth to generate a second quantized mesh; and encoding the second quantized mesh into a bitstream. According to one or more embodiments, an encoder comprises: at least one memory configured to store program code; and at least one processor configured to read the program code and operate as instructed by the program code, the program code including: extraction code configured to cause the at least one processor to extract from an input mesh an extracted half symmetry mesh, the input mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted half symmetry mesh comprising one of the first side and the second side, first quantization code configured to cause the at least one processor to quantize the extracted half symmetry mesh at a first bitdepth to generate a first quantized mesh, reparameterization code configured to cause the at least one processor to reparameterize the first quantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh, second quantization code configured to cause the at least one processor to quantize the reparameterized mesh at a second bitdepth different from the first bitdepth to generate a second quantized mesh, and encoding code configured to cause the at least one processor to encode the second quantized mesh into a bitstream. According to one or more embodiments, a non-transitory computer readable medium having instructions stored therein, which when executed by a processor in an encoder cause the encoder to execute a method comprising: extracting from an input mesh an extracted half symmetry mesh, the input mesh comprising a first side and a second side, the second side being opposite to the first side, the extracted mesh comprising one of the first side and the second side; quantizing the extracted half symmetry mesh at a first bitdepth to generate a first quantized mesh; reparameterizing the first quantized mesh to generate a reparameterized mesh that includes a reduction in one or more empty spaces in the first quantized mesh; quantizing the reparam